The present invention relates to an apparatus and method for forming grooves or slots in concrete roadways and airport runway pavements. High-speed travel on smooth, slick concrete roadways is often hazardous when the roadways are wet. Water lays upon the roadway in a surface film and the tires of a vehicle or airplane tend to skim along the surface of the water thereby reducing friction against the road. This effect is commonly known as hydroplaning. The effect of braking and skid control are substantially reduced, if not eliminated, during hydroplaning.
To eliminate or substantially reduce hydroplaning and loss of control, it is imperative to reduce the amount of water standing on the surface of the roadways. One method which has been effective in this regard is to provide a plurality of parallel, closely-spaced grooves or slots in the concrete pavement, the grooves running either longitudinally or transversely to the direction of travel. The grooves provide escape routes from the upper surface of the roadway for the water, thereby leaving less water on the upper road surface for the tires to contact.
The usual method of providing the slots or grooves is by cutting them in the finished roadway with diamond tipped cutters. The concrete is allowed to harden and the grooves are then cut to the desired depth (about one-eighth to one-fourth of an inch). Electronic sensors and feeler gauges are used to automatically guide the cutting machines and readjust the blades to the required depth. Forming slots or grooves in concrete with this method is slow and expensive and requires cumbersome, complicated and expensive machinery. Also, it is often not possible to slot the entire width of a roadway at one time, thus necessitating numerous passes in the same lane with the grooving machine. Additionally, the cutting often produces cracks or ruptures in the concrete surface causing the roadway to subsequently deteriorate and fracture. Moreover, due to the expense involved and the disruption of traffic in order to cut the grooves, the grooves on highways often are placed only at the most dangerous portions of a roadway, such as on sharp curves. The dangerous skidding conditions thus are allowed to remain on the remainder of the roadway.
It has also been attempted to provide the necessary grooves in the concrete surfaces prior to the final setting of the roadway. For example, in U.S. Pat. Nos. 3,516,339 and 3,703,857, different apparatus are disclosed which form grooves or slots in a concrete roadway by drawing over freshly-laid concrete a plurality of molding bars or flexible rods spaced closely together. It is doubtful, however, whether the apparatus and methods shown in these two patents would achieve uniform and consistent results throughout the length of the concrete roadway due to the various textures and stages of setting of the concrete at various points in the roadway. Moreover, since the concrete has to be sufficiently flowable or liquid at the time of the formation of the grooves to allow the grooves to be formed therein, it is also sufficiently flowable to allow some of the concrete to return into the formed grooves after the grooving rods have passed and to round off the edges of the grooves. This creates a less effective surface for reducing or eliminating skidding conditions. A similar grooving and brooming process is disclosed in U.S. Pat. No. 3,605,579.
An object of the present invention is to provide an improved method and apparatus for forming grooves or slots in concrete roadways. Another object of the present invention is to provide grooves or slots in concrete roadways which are precisely and accurately shaped and thus provide better and more efficient grooves for reducing and eliminating skidding conditions.
In accordance with the present invention, the present apparatus and method provide a sheet of flexible material, such as a fiber-reinforced plastic or elastomer, with a plurality of parallel, closely-spaced ribs on one surface thereof. The ribs are provided either longitudinally or transversely on the sheet. The sheet is positioned on the surface of a freshly poured concrete roadway and the ribs thereon are impressed into the surface. The flexible sheet is placed on the concrete by unrolling it from a spool mounted on a construction vehicle. The sheet is allowed to remain on the roadway until the concrete is set and dry. It is then removed by rolling it back onto the spool revealing the grooves. If desired, holes can be provided in the sheet to hasten the drying of the concrete.
Other objects, features and aspects of the invention will become apparent from the following description and claims when viewed in accordance with the accompanying drawings.